Journal of Radiation Protection and Research

The Korean Association for Radiation Protection (대한방사선방어학회)
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EQUIVALENT DOSE FROM SECONDARY NEUTRONS AND SCATTER PHOTONS IN ADVANCE RADIATION THERAPY TECHNIQUES WITH 15 MV PHOTON BEAMS

  • Ayuthaya, Isra Israngkul Na (Department of Nuclear Engineering, Faculty of Engineering, Chulalongkorn University and Division of Radiology, Faculty of Radiation Oncology, King Chulalongkorn Memorial Hospital) ;
  • Suriyapee, Sivalee (Department of Radiology, Faculty of Medicine, Chulalongkorn University) ;
  • Pengvanich, Phongpheath (Department of Nuclear Engineering, Faculty of Engineering, Chulalongkorn University)
  • Received : 2015.06.18
  • Accepted : 2015.09.08
  • Published : 2015.09.30
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Abstract

The scatter photons and photoneutrons from high energy photon beams (more than 10 MV) will increase the undesired dose to the patient and the staff working in linear accelerator room. This undesired dose which is found at out-of-field area can increase the probability of secondary malignancy. The purpose of this study is to determine the equivalent dose of scatter photons and neutrons generated by 3 different treatment techniques: 3D-conformal, intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). The measurement was performed using two types of the optically stimulation luminescence detectors (OSL and OSLN) in the Alderson Rando phantom that was irradiated by 3 different treatment techniques following the actual prostate cancer treatment plans. The scatter photon and neutron equivalent dose were compared among the 3 treatments techniques at the surface in the out-of-field area and the critical organs. Maximum equivalent dose of scatter photons and neutrons was found when using the IMRT technique. The scatter neutrons showed average equivalent doses of 0.26, 0.63 and $0.31mSv{\cdot}Gy^{-1}$ at abdominal surface region which was 20 cm from isocenter for 3D, IMRT and VMAT, respectively. The scattered photons equivalent doses were 6.94, 10.17 and $6.56mSv{\cdot}Gy^{-1}$ for 3D, IMRT and VMAT, respectively. For the 5 organ dose measurements, the scattered neutron and photon equivalent doses in out of field from the IMRT plan were highest. The result revealed that the scatter equivalent doses for neutron and photon were higher for IMRT. So the suitable treatment techniques should be selected to benefit the patient and the treatment room staff.

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References

  1. Chibani O, Ma CC. Photonuclear dose calculations for high-energy photon beams from Siemens and Varian linacs. Med Phys. 2003;30:1990-2000. https://doi.org/10.1118/1.1590436
  2. Followill D, Gies P, Boyer A. Estimates of wholebody equivalent produced by beam intensity modulated conformal therapy. Int J Radiat Oncol Bio Phys. 1997; 38(3):667-672. https://doi.org/10.1016/S0360-3016(97)00012-6
  3. Reft CS, Runkel-Muller R, Myrianthopoulos L. In vivo and phantom measurements of the secondary photon and neutron doses for prostate patients undergoing 18 MV IMRT. Med Phys. 2006;33(10): 3734-3742. https://doi.org/10.1118/1.2349699
  4. Howell RM, Kry SF, Burgett E, et al. Secondary neutron spectra from modern Varian, Siemens, and Elektalinacs with multileaf collimators. Med Phys. 2009;36(9):4027-4038. https://doi.org/10.1118/1.3159300
  5. Nedaie HA, Darestani H, Banaee N, et al. Neutron dose measurements of Varian and Elektalinacs by TLD600 and TLD700 dosimeters and comparison with MCNP calculations. Med Phys. 2014;39(1): 10-17. https://doi.org/10.4103/0971-6203.125476
  6. Passmore C, Kirr M. Neutron response characterization of an OSL neutron dosimeter. Radiat Prot Dosim. 2011;144:155-160. https://doi.org/10.1093/rpd/ncq300
  7. Martinez-Ovalle SA, Rarquero R, Gomez-Ros JM, et al. Ambient neutron equivalent dose outside concrete vault rooms for 15 and 18 MV radiotherapy accelerators. Radiat Prot Dosim. 2012;148 (4):457-464. https://doi.org/10.1093/rpd/ncr208
  8. Bednarz B, Xu XG. Monte carlo modeling of a 6 and 18 MV Varian Clinac medical accelerator for in-field and out-of-field dose calculations: development and validation. Phys Med Biol. 2009;54(4): 43-57.
  9. Meo XS, Kase KR, Liu LC, et al. Neutron sources in the Varian Clinac 2100C/2300C medical accelerator calculated by the EGS4 code. Health Phys. 1997;72:524-530. https://doi.org/10.1097/00004032-199704000-00003
  10. Cygler JE, Yukihara E. Optically Stimulated Luminescence (OSL) dosimetry in radiotherapy. AAPM 51th annual meeting, California. 2009.
  11. ICRP (2007), The 2007 recommendation of ICRP. Annals of the ICRP, ICRP Publication 103.
  12. Schneider U, Walsh L. Cancer risk estimates from the combined Japanese A-bomb and Hodgkin cohorts for doses relevant to radiotherapy. Radiat Environ Biophys. 2008;47:253-263. https://doi.org/10.1007/s00411-007-0151-y
  13. Yoon M, Ahn SH, Kim J, et al. Radiation-induced cancers from modern radiotherapy techniques: intensity-modulated radiotherapy versus proton therapy. Int J Radiat Oncol Biol Phys. 2010;77(5): 1477-1485. https://doi.org/10.1016/j.ijrobp.2009.07.011
  14. Kry SF, Salehpour M, Followill D, et al. Out-offield photon and neutron equivalent doses from step-and-shoot intensity-modulated radiation therapy. Int J Radiat Oncol Bio Phys. 2005;62(4):1204-1216. https://doi.org/10.1016/j.ijrobp.2004.12.091
  15. Zabihzadeh M, Ay MR, Allahverdi M, et al. Monte Carlo estimation of photoneutrons contamination from high-energy x-ray medical accelerators in treatment room and maze: a simplified model. Radiat Prot Dosim. 2009;135(1):21-32. https://doi.org/10.1093/rpd/ncp097